1. Field of the Invention
The present invention relates in general to a honing apparatus for honing internal or external cylindrical surfaces of a workpiece, and more particularly to a technique for improving the honing accuracy.
2. Discussion of the Prior Art
A honing apparatus or machine for finishing internal or external cylindrical surfaces of a workpiece to a relatively high degree of accuracy and smoothness generally includes (a) a honing head which supports abrasive honing stones or sticks such that the honing stones are opposed to the cylindrical surface of the workpiece and are movable substantially in a radial direction of the cylindrical surface, (b) a changing mechanism associated with the honing head, for changing either the radial position of the honing stones or the pressure of contact between the honing stones and the cylindrical surface, (c) a first drive device for effecting a relative reciprocating movement between the honing head and the workpiece, and (d) a second drive device for effecting a relative rotating movement between the honing head and the workpiece.
In the honing apparatus of the type indicated above, the honing stones are given by the first and second drive devices concurrent movements in both circumferential and axial directions of the cylindrical surface of the workpiece while the stones are held in contact with the cylindrical surface. At the same time, the honing stones are given by the changing mechanism a feed movement in the radial direction of the cylindrical surface, or a contact pressure against the cylindrical surface. It is recognized that the cylindricity, roundness, smoothness and other accuracy values of the honed surface are greatly influenced by the honing conditions such as the axial reciprocating range and speed of the honing stones relative to the workpiece, the rotating speed of the honing stones relative to the workpiece, and the radial feed rate of the stones or contact pressure of the stones against the workpiece surface. To hone the workpiece surface to sufficiently high degrees of accuracy and smoothness with high honing efficiency, the first and second drive devices and the changing mechanism should be accurately controlled with an excellent level of operating response.
Laid-open Publication No. 59-93859 of unexamined Japanese Utility Model Application discloses a honing apparatus which uses electrically operated motors as drive sources of the second drive device and the changing mechanism as indicated above. However, the publication is silent about the type of the drive source of the first drive device for reciprocating movement between the honing head and the workpiece. However, the known arrangements usually employ a hydraulically operated actuator as the drive source of the first drive device.
To improve the honing accuracy and honing efficiency, the first drive device should be precisely controlled to control the relative axial reciprocating movement of the honing stones in response to the actual conditions of the workpiece surface in the process of being honed. However, the hydraulically operated actuator conventionally used for the first drive device is difficult to control for regulating the range and speed of the relative reciprocating movement between the honing stones and the workpiece, with a short response to the varying conditions of the workpiece surface.